Thank you for your supports again.
Definitive I do NOT have older data on my fresh, clean, virgin
hard disk (that's a fact).
I agree with Gerald, that the loop loader produce the problem. Unfortunately the problem doesn't appear with TC 3.7 or TC 3.8.4 (I added the TC 4.3 to my stick ... and the rest of the story fills this thread).
@Markus: You're right, documentation is a good chioce
But imagine that two ISOs do the job but a third one did not (same stick, same environment, but other versions). And additionaly notice: The thread started with the same problem by an other member.
Hope others have also learned something from that.